Thermal spin fluctuations in spinor Bose-Einstein condensates

TL;DR

This paper investigates thermal spin fluctuations in spinor Bose-Einstein condensates, demonstrating their potential for ultra-low temperature thermometry and adiabatic cooling strategies.

Contribution

It provides a detailed analysis of thermal activation mechanisms in different spinor BECs and explores their application in precise thermometry and cooling.

Findings

Thermal spin fluctuations enable thermometry at extremely low temperatures.

Spin fluctuations depend on spin-changing collisions and dipole-induced relaxation.

Entropy behavior suggests potential for adiabatic cooling in spinor BECs.

Abstract

We study the thermal activation of spin fluctuations in dynamically-stable spinor Bose-Einstein condensates. We analyze the specific cases of a non-dipolar spin-1 condensate in m = 0, where thermal activation results from spin-changing collisions, and of a Chromium condensate in the maximally stretched state m = -3, where thermal spin fluctuations are due to dipole-induced spin- relaxation. In both cases, we show that the low energy associated to the spinor physics may be employed for thermometry purposes down to extremely low temperatures, typically impossible to measure in BECs with usual thermometric techniques. Moreover, the peculiar dependence of the system's entropy with the applied Zeeman energy opens a possible route for adiabatic cooling.